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Simulation of a calendernip
2000 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The calendering process is made in order to improve the printing properties of paper products. The paper web is compressed in one or several roll nips, usually after the drying or coating section. The aim of this study was to develop a method to simulate a calender nip. This in order to have a method to simulate a supercalender nip and to be able to try different rollcovers in easily. The simulations have been compared with supercalendered and laboratory calendered papers, and approximate values of the dwell time in the nip have been calculated. A comparison of these values with the estimated dwell time from the platen press shows the platen press is comparable with a supercalender. The dwell time in the laboratory calender is much longer because of the slower speed. This thesis work is also an evaluation of the developed method. In the simulation trials SC-paper with a grammage of 56 g/m2 were used. It was found that the developed platen press is capable to simulate a supercalender nip in some areas. The simulation trial indicates there is a correlation between the platen press and a supercalender nip. The maximum pressure achieved with the platen press is comparable with the maximum pressures for the laboratory calender and the supercalender at SCA Graphic Ortviken in Sundsvall. The reason to the comparison with the supercalender at SCA Graphic Ortviken is that the information about their supercalender was easy to achieve and it was possible to measure the properties of the rolls. The evaluation of the simulation trials has been made with the program MODDE. An experimental design was used for the trials and the multivariate study was evaluated with a PLS model. The PLS-model shows that the optical properties are difficult to explain but the density, thickness, gloss and surface roughness could be quite well explained. The most important variable for the responses is the type of material in the rollcovers. Subsequently comes the number of nips, moisture content in the paper and the nip pressure. The temperature of the punch has not a great effect on the paper properties as was expected. The reason for this is probably because the heat transfer between the punch and the paper is not good enough. The gloss values obtained in this simulation trial are low compared to supercalendered paper. This gives an indication that the enhancement of the paper gloss is maybe due to microslipping in the supercalender nip. Can also depend on the low heat transfer in the simulation.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Calendering, Calendernip, Supercalender, Pressurepulse, Papergloss, Paperproperties, Microslipping
Keyword [sv]
URN: urn:nbn:se:ltu:diva-57099ISRN: LTU-EX--00/251--SELocal ID: dcd24757-0a94-449e-8dca-9fea15b80f01OAI: diva2:1030486
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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